Fix exporters deployment error

On compute nodes we get:
cmp01.virtual-mcp11-contrail.local:
----------
          ID: libvirt_exporter_service
    Function: service.running
        Name: libvirt-exporter
      Result: False
     Comment: The following requisites were not found:
                                 watch:
                                     file: libvirt_exporter_service_config_file

Change-Id: I31069ec37702f8466da27b76c0becc6802cea272

prometheus/exporters.sls

@@ -6,7 +6,6 @@
   pkg.installed:
     - names: {{ parameters.packages }}
     {%- endif %}
-  {%- endif %}
 
 {{ exporter }}_exporter_service:
   service.running:
@@ -15,8 +14,10 @@
     {%- if grains.get('noservices') %}
     - onlyif: /bin/false
     {%- endif %}
+    {%- if parameters.template is defined %}
     - watch:
       - file: {{ exporter }}_exporter_service_config_file
+    {%- endif %}
 
     {%- for svc, svc_parameters in parameters.get('services', {}).iteritems()  %}
       {%- if  svc_parameters.get('enabled', False) %}
@@ -61,4 +62,5 @@
         {%- endif %}
       {%- endif %}
     {%- endfor %}
+  {%- endif %}
 {%- endfor %}